The 41-year-old led the Saints to the Scottish Championship title this season, but the lure of one of England's biggest clubs looks to have proved too big.
Despite their relegation to League One, the future finally looks bright for Sunderland following Stewart Donald's takeover - and subsequent promise of substantial funds - at the Stadium of Light.
But which players will Ross target if he takes over? Could a Celtic player feature on his wishlist?
HITC Sport has dug up three likely options...
Harry Davis (St Mirren)
Davis has been one of Ross's key players since he made the move north of the border from Crewe, for whom he played for four seasons at League One level. A new centre-back could be required at Sunderland, to cover the likely departures of Lamine Kone, John O'Shea and Marc Wilson. And Davis, whose contract expires this summer, would not cost them a penny.
A star under Ross last season, Mallan has failed to kick on since leaving for Barnsley, for whom he has made just nine appearances. A drop down a level could be good for the midfielder, however - although, with the Tykes heading for the third tier themselves, Sunderland could struggle to prise him away. Hibernian have shown an interest, according to reports in Scotland.
Lewis Morgan (Celtic)
St Mirren's standout performer in 2017-18, Morgan earned himself a January move to Celtic before being loaned back to the Paisley side to finish what he had started. The winger scored 14 goals and assisted nine en route to the title and is targeting an impact at Celtic Park next season. The Bhoys may prefer him to continue his development elsewhere, however, in which case a reunion with Ross at Sunderland could suit all parties.
Should Sunderland make moves for the St Mirren, Barnsley and Celtic players this summer?
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